Magnetic and transport properties of electronically spin polarised double perovskites and Heusler intermetallics

10.26686/wgtn.17142857 ◽

2021 ◽

Author(s):

◽

Jibu Stephen

Keyword(s):

Magnetic Field ◽

Thin Films ◽

Heusler Alloys ◽

Antiferromagnetic Coupling ◽

Double Perovskites ◽

Half Metallic ◽

Electronic Spin ◽

Disordered Films ◽

Spin Polarisation ◽

Curie Temperatures

<p>Half-metallic ferromagnets with 100 % electronic spin polarisation are an interesting class of materials for new spin transport electronics applications. Some of the double perovskites and Heusler alloys are predicted to be half-metallic with Curie temperatures above room temperature. This thesis presents the results from an experimental study of polycrystalline double perovskites Sr₂₋ₓLaₓFeMoO₆ and Ba₂₋ₓLaₓFeMoO₆, and ordered and disordered epitaxial thin films of Co₂MnSi Heusler alloys. A magnetothermopower was observed in Sr₂₋ₓLaₓFeMoO₆ and Ba₂₋ₓLaₓFeMoO₆. This magnetothermopower can be explained in terms of a spin-tunnelling contribution to the thermopower between grains that changes in an applied magnetic field. The results from the high temperature (above 400 K) magnetisation studies on Ba₂₋ₓLaₓFeMoO₆ in the paramagnetic region reveal that a localised electron model with antiferromagnetic coupling to itinerant electrons can account for the carrier concentration dependent effective moments. The correlation between the bare itinerant electron susceptibility and the Curie-Weiss temperature supports the kinetic energy driven model that has been used to account for the electronic spin polarisation and high Curie temperatures. Antisite disorder is evident in the Co₂MnSi thin films that leads to a reduction in the saturation magnetisation. The resistivity of the ordered Co₂MnSi thin film is linear in temperature whereas the resistivity of the disordered film increases at low temperature due to weak localisation. A magnetoresistance is observed in ordered and disordered films. At low fields (below 0.1 T) the magnetoresistance is likely to be due to domain wall scattering. For magnetic fields greater than 0.1 T there is likely to be a contribution from a magnetic-field-induced suppression of the weak localisation resistivity. Similar magnetoresistance behaviour was observed for ordered and disordered films. There is a large anomalous Hall resistivity observed in the ordered and disordered Co₂MnSi thin films. In the case of the ordered film it is found that the anomalous Hall effect is dominated by skew scattering.</p>

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First-principles study of exchange interactions and Curie temperatures of half-metallic ferrimagnetic full Heusler alloys Mn2V Z (Z = Al, Ge)

Journal of Physics Condensed Matter ◽

10.1088/0953-8984/17/6/017 ◽

2005 ◽

Vol 17 (6) ◽

pp. 995-1001 ◽

Cited By ~ 67

Author(s):

E Şaşioglu ◽

L M Sandratskii ◽

P Bruno

Keyword(s):

First Principles ◽

Heusler Alloys ◽

Exchange Interactions ◽

Half Metallic ◽

First Principles Study ◽

Full Heusler ◽

Full Heusler Alloys ◽

Curie Temperatures

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Martensitic Transformation and Metamagnetic Transition in Co-V-(Si, Al) Heusler Alloys

Metals ◽

10.3390/met11020226 ◽

2021 ◽

Vol 11 (2) ◽

pp. 226

Author(s):

Kousuke Nakamura ◽

Atsushi Miyake ◽

Xiao Xu ◽

Toshihiro Omori ◽

Masashi Tokunaga ◽

...

Keyword(s):

Magnetic Field ◽

Martensitic Transformation ◽

Spontaneous Magnetization ◽

Heusler Alloys ◽

Parent Phase ◽

Entropy Change ◽

Ferromagnetic State ◽

Martensite Phase ◽

Reverse Martensitic Transformation ◽

Curie Temperatures

This study investigates the crystal structure, martensitic transformation behavior, magnetic properties, and magnetic-field-induced reverse martensitic transformation of Co64V15(Si21–xAlx) alloys. It was found that by increasing the Al composition, the microstructure changes from the martensite phase to the parent phase. The crystal structures of the martensite and parent phases were determined as D022 and L21, respectively. Thermoanalysis and thermomagnetization measurements were used to determine the martensitic transformation and Curie temperatures. Both the ferromagnetic state of the parent phase and that of the martensite phase were observed. With the increasing Al contents, the martensitic transformation temperatures decrease, whereas the Curie temperatures of both the martensite and parent phases increase. The spontaneous magnetization and its composition dependence were also determined. The magnetic-field-induced reverse martensitic transformation of a Co64V15Si7Al14 alloy under pulsed high magnetic fields was observed. Moreover, using the results of the DSC measurements and the pulsed high magnetization measurements, the temperature dependence of the transformation entropy change of the Co-V-Si-Al alloys was estimated.

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Martensite-austenite and Ferromagnetic-paramagnetic Transformations in Ni2-xAxMn1-yByGa1-zCz (A, B=Co; C=Al) Heusler Alloys

Revista de Chimie ◽

10.37358/rc.08.12.2058 ◽

2009 ◽

Vol 59 (12) ◽

Author(s):

Mihail-Liviu Craus ◽

Viorel Dobrea ◽

Mihai Lozovan

Keyword(s):

Magnetic Field ◽

Transition Temperature ◽

Martensitic Transformation ◽

Low Temperatures ◽

Room Temperature ◽

Heusler Alloys ◽

Partial Substitution ◽

Martensitic Transition ◽

Cscl Type ◽

Curie Temperatures

Ni2MnGa Heusler alloy is known as a potential smart material. At room temperature it has a L21 type structure, undergoing a martensitic transition (TM) at low temperatures. Some authors have classified Ni-Mn-Ga Heusler alloys on the values of martensitic transformation and Curie temperatures: first group formed by alloys with TM below room temperature and TC, second group with TM around room temperature and third group with TM]TC. The partial substitution of Ni with Mn leads to an increase of the transition temperature and a decrease of the Curie temperature. The Ni2-xMn1+xGa alloys have a complex tetragonal structure at room temperature. The substitution of Ga with Al can change the crystalline and magnetic structure of Heusler alloys: Ni2MnAl is antiferromagnetic for a B2 (CsCl type, with Mn and Al randomly distributed in the center of the cube) structure and ferromagnetic for a L21 (BiF3 type with Mn and Al ordered distributed in the cube center) structure. We intend to put in evidence a dependence between the applied magnetic field on a side, and the transition temperature, on other side, for the Ni2-xAxMn1-yByGa1-zCz (A, B=Co; C=Al) Heusler alloys.

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The electronic, half-metallic, elastic, and magnetic properties of new PtWZ (Z= In, Tl, Sn, and Pb) half-Heusler alloys via GGA and GGA+mBJ methods

Physica Scripta ◽

10.1088/1402-4896/ac3fcd ◽

2021 ◽

Author(s):

Evren Görkem Özdemir ◽

Semih Doğruer

Keyword(s):

Magnetic Properties ◽

Magnetic Moments ◽

Heusler Alloys ◽

Band Gaps ◽

First Principle ◽

Full Agreement ◽

Half Metallic ◽

First Principle Calculations ◽

Direct Band ◽

Curie Temperatures

Abstract The first-principle calculations of PtWZ (Z= In, Tl, Sn, and Pb) half-Heusler alloys were calculated by WIEN2k for GGA and GGA+mBJ methods. First, the ferromagnetic (FM) phases were obtained more energetically stable than non-magnetic (NM) and antiferromagnetic (AFM) phases in each alloy. The Curie temperatures of PtWIn, PtWTl, PtWSn, and PtWPb alloys were obtained as 286.98 K, 467.14 K, 721.98 K, and 1114.31 K, respectively, by utilizing the energy differences of the AFM and FM phases. In each method and alloy used, spin-up electrons showed metallic character. In the GGA method, PtW(In, Tl) alloys have direct band gaps of 0.72044 eV and 0.91488 eV in spin-down electrons, while PtW(Sn, Pb) alloys have indirect band gaps of 1.2558 eV and 1.11892 eV, respectively. In the GGA+mBJ method, the bandgap directions in all compounds remained the same. Here, band gaps in PtW(In, Tl, Sn, and Pb) alloys were obtained as 0.99918 eV, 1.15385 eV, 1.42676 eV, and 1.17497 eV, respectively. While the total magnetic moment values of PtW(In, Tl) half-Heusler alloys were obtained as 1.00 μB/f.u., the total magnetic moments of PtW(Sn, Pb) alloys were obtained as 2.00 μB/f.u. These results are in full agreement with the Slater-Pauling rule. According to elastic calculations, PtWIn, PtWTl, PtWSn, and PtWPb half-Heusler alloys are elastically stable and ductile.

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The impact on the magnetic field growth of half-metallic Fe3O4 thin films

Journal of Solid State Chemistry ◽

10.1016/j.jssc.2006.04.007 ◽

2006 ◽

Vol 179 (6) ◽

pp. 1618-1622 ◽

Cited By ~ 9

Author(s):

Xiao-Li Tang ◽

Huai-Wu Zhang ◽

Hua Su ◽

Zhi-Yong Zhong ◽

Yu-lan Jing

Keyword(s):

Magnetic Field ◽

Thin Films ◽

Half Metallic ◽

Field Growth ◽

The Impact ◽

The Magnetic Field

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Electrical Anisotropy of Thin Metal Films Growing on Dielectric Substrates

Nonlinear Analysis Modelling and Control ◽

10.15388/na.2002.7.2.15193 ◽

2002 ◽

Vol 7 (2) ◽

pp. 45-52

Author(s):

L. Jakučionis ◽

V. Kleiza

Keyword(s):

Magnetic Field ◽

Thin Films ◽

Uniaxial Anisotropy ◽

Metal Films ◽

Thin Layers ◽

Electrical Anisotropy ◽

Electrical Field ◽

Dielectric Substrates ◽

Unequal Probability ◽

Conductive Thin Films

Electrical properties of conductive thin films, that are produced by vacuum evaporation on the dielectric substrates, and which properties depend on their thickness, usually are anisotropic i.e. they have uniaxial anisotropy. If the condensate grow on dielectric substrates on which plane electrical field E is created the transverse voltage U⊥ appears on the boundary of the film in the direction perpendicular to E. Transverse voltage U⊥ depends on the angle γ between the applied magnetic field H and axis of light magnetisation. When electric field E is applied to continuous or grid layers, U⊥ and resistance R of layers are changed by changing γ. It means that value of U⊥ is the measure of anisotropy magnitude. Increasing voltage U0 , which is created by E, U⊥ increases to certain magnitude and later decreases. The anisotropy of continuous thin layers is excited by inequality of conductivity tensor components σ0 ≠ σ⊥. The reason of anisotropy is explained by the model which shows that properties of grain boundaries are defined by unequal probability of transient of charge carrier.

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FIRST-PRINCIPLES STUDY OF MAGNETISM AND HALF-METALLIC PROPERTIES OF THE D0 QUATERNARY HEUSLER ALLOYS BANYO (Y = K, RB AND CS)

Письма в Журнал экспериментальной и теоретической физики ◽

10.31857/s123456782012006x ◽

2020 ◽

Vol 111 (11-12(6)) ◽

pp. 819-819

Author(s):

S. BENATMANE ◽

S. CHERID

Keyword(s):

First Principles ◽

Heusler Alloys ◽

Half Metallic ◽

First Principles Study ◽

Quaternary Heusler Alloys

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Effects of Perpendicular Magnetic Field Annealing on the Structural and Magnetic Properties of [Co/Ni]2/PtMn Thin Films

Magnetochemistry ◽

10.3390/magnetochemistry7030038 ◽

2021 ◽

Vol 7 (3) ◽

pp. 38

Author(s):

Roshni Yadav ◽

Chun-Hsien Wu ◽

I-Fen Huang ◽

Xu Li ◽

Te-Ho Wu ◽

...

Keyword(s):

Magnetic Field ◽

Thin Films ◽

Magnetic Properties ◽

Photoelectron Spectroscopy ◽

Perpendicular Magnetic Field ◽

Face Centered Cubic ◽

Lattice Image ◽

X Ray ◽

Field Annealing ◽

Face Centered

In this study, [Co/Ni]2/PtMn thin films with different PtMn thicknesses (2.7 to 32.4 nm) were prepared on Si/SiO2 substrates. The post-deposition perpendicular magnetic field annealing (MFA) processes were carried out to modify the structures and magnetic properties. The MFA process also induced strong interlayer diffusion, rendering a less sharp interface between Co and Ni and PtMn layers. The transmission electron microscopy (TEM) lattice image analysis has shown that the films consisted of face-centered tetragonal (fct) PtMn (ordered by MFA), body-centered cubic (bcc) NiMn (due to intermixing), in addition to face-centered cubic (fcc) Co, Ni, and PtMn phases. The peak shift (2-theta from 39.9° to 40.3°) in X-ray diffraction spectra also confirmed the structural transition from fcc PtMn to fct PtMn after MFA, in agreement with those obtained by lattice images in TEM. The interdiffusion induced by MFA was also evidenced by the depth profile of X-ray photoelectron spectroscopy (XPS). Further, the magnetic properties measured by vibrating sample magnetometry (VSM) have shown an increased coercivity in MFA-treated samples. This is attributed to the presence of ordered fct PtMn, and NiMn phases exchange coupled to the ferromagnetic [Co/Ni]2 layers. The vertical shift (Mshift = −0.03 memu) of the hysteresis loops is ascribed to the pinned spins resulting from perpendicular MFA processes.

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